A number of analytical procedures and devices are commonly used to test body fluids for the presence of substances of diagnostic value. Blood and urine are the body fluids of choice. An advantage of blood as a test fluid is that analytes are often at relatively high concentrations, and measurements of these concentrations can often provide information about a patient's health. Urine is useful for diagnostic testing when the blood component of interest (e.g., a low molecular weight drug or hormone) is concentrated during urine formation. However, the urine concentration of an analyte does not usually reflect the physiologically active amount of the analyte in blood.
Although saliva is not commonly used as a body fluid in medical diagnosis, numerous studies (Parry, et al.; Thieme, et al., 1992 a,b) have demonstrated that saliva and other types of oral fluid can provide a reliable sample for diagnostic testing involving antibodies or antigens specific for various human or animal pathogens. Oral fluids have also been shown to be useful in measuring the body levels of naturally occurring hormones or therapeutic and other drugs.
One advantage of sampling oral fluid over sampling blood and urine is the convenience of obtaining the sample. A trained phlebotomist is not required, as is the case with blood, nor are special arrangements for privacy-in-collection and custody of the sample required, as is the case with urine. Furthermore, collection of an oral fluid sample obviates the hazard of handling blood-contaminated needles and tubes.
Devices for the collection of oral fluid have been described. U.S. Pat. Nos. 4,418,702 and 4,580,577 show an absorbent pad for absorbing oral fluid, and a barrel-piston arrangement for extracting the fluid from the pad.
U.S. Pat. No. 4,774,962 describes an absorbent pad for absorbing saliva, and a centrifuge tube and tube-insert for removing oral fluid from the pad by centrifugation.
U.S. Pat. No. 5,056,521 describes an apparatus for use in monitoring glucose in oral fluid. The apparatus includes a barrel-piston arrangement having a nonreactive absorbent swab secured to the piston. The barrel and piston are used to squeeze the fluid sample from the swab into a glucose monitoring instrument.